package Week2.J0425;

import java.util.Scanner;

public class 过河卒_xv {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int x = scanner.nextInt();
        int y = scanner.nextInt();

        int[][] board = new int[n+2][m+2];
        board[0][1] = 1;
        x++;
        y++;

        for (int i = 1; i <= n+1; i++) {
            for (int j = 1; j <= m+1; j++) {
                if (i != x && j != y && Math.abs(i-x) + Math.abs(j-y) == 3
                        ||(i == x && j == y)) {
                    board[i][j] = 0;
                }else {
                    board[i][j] = board[i-1][j] + board[i][j-1];
                }
            }
        }
        System.out.println(board[n+1][m+1]);
    }
}
